/Engine/Source/Runtime/SlateCore/Public/Widgets/SWidget.h
Called whenever a focus path is changing on all the widgets within the old and new focus paths
virtual void OnFocusChanging ( const [FWeakWidgetPath](API\Runtime\SlateCore\Layout\FWeakWidgetPath) & PreviousFocusPath, const [FWidgetPath](API\Runtime\SlateCore\Layout\FWidgetPath) & NewWidgetPath, const [FFocusEvent](API\Runtime\SlateCore\Input\FFocusEvent) & InFocusEvent )